No, 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 415 
in Figs. 28-30 is a longitudinal division of univalent chromo- 
somes. On this assumption synapsis is coincident with 
synizesis and, at the stage of Figs. 33-34, the nucleus contains 
twelve bivalent chromosomes which are divided longitudi- 
nally. This is the interpretation which Janssens has given to 
the early post-synizesis stages which he finds in the ege of 
Triton. The fact that in later growth stages the great major- 
ity of the chromosomes are not arranged in pairs makes this 
interpretation improbable for the egg of Bufo, since in the 
eggs of other forms when bivalent chromosomes divide longi- 
tudinally the parts remain together or are connected in some 
Way. 
If we assume that two chromosomes united side by side 
in the spireme, then the subsequent longitudinal splitting of 
the spireme is merly a separation of the chromosomes that 
were previously paired, and the transverse division of the 
spireme is the means by which the chromosomes are com- 
pletely separated from each other. Synapsis, on this as- 
sumption, does not necessarily occur during synizesis, since 
the somatic number of chromosomes is evolved from the 
spireme. I am inclined to believe that synizesis in the ege of 
Bufo is a process by which the chromatin which bears the 
hereditary qualities and is to be used for the chromosomes of 
the maturation spindle is separated from the chromatin which 
has other uses in the cell. This would seem to bear out 
Gardiner’s (33) contention that “there are two kinds of 
chromatin stuff, the one insoluble and bearing the heredity 
which is to be transmitted to the daughter-cells, the other 
food for the cytoplasm.” If this interpretation of synizesis 
is correct, the chromosomes must have been united in pairs in 
the spireme that was evolved from the synizesis stage, but 
synapsis does not take place until the beginning of the matu- 
ration period. This interpretation seems the more probable 
since Jordan failed to find a pairing of the chromosomes in 
the ovarian egg of the newt at any stage of development. 
‘The second period when it is impossible to trace the history 
of the chromatin occurs just previous to the formation of the 
